I'm 35 yrs old. For 20 years my cycle usually runs 29 - 30 days like clockwork. My last two periods were 5& 3 days early. When my next one was late I took a pregnancy test each day for 3 days. All were negative. One week later I took one and it was positive. With my other pregnancies I tested positive before i was even late. I wasn't active during the time when I usually ovulate. I'm wondering what is going on? Could zpak effect ovulation? Could the negative tests mean I ovulated late?

Hi Klantgen,Thanks for your question.Antibiotics & the illness for which they are used both may effect your menstrual cycle. Pregnancy test may take some time to come positive depending upon the hormone levels in your body & the ovulation time may also vary. It is not always fixed. All pregnancies are different it is not necessary to have the same results every time. Sometimes these tests are also falsely negative. Sperms may also stay alive in your body for 3-5 days.I have given you a number of possible reasons. Don't let these details confuse you. Just take good care of yourself & start taking folic acid supplements.Please write back if you want to discuss this further.Best regards

Hi,Welcome back.In the first trimester ultrasound can determine this with an accuracy of 5-7 days.Accuracy also depends on the experience of the sonologist & better for trans-vaginal ultrasound.This will tell you the time when you conceived with an accuracy of 5-7 days.Take care